Using Drugs to Prevent HIV Infection: Who, What, and When?
Using Drugs to Prevent HIV Infection: Who, What, and When?
Medscape: How do we educate potential PrEP candidates about the importance of adherence?
Dr. Cohen: All we can do is educate individuals about what we've learned from the trials that were done. The PrEP trials demonstrated the biological plausibility that continually bathing the tissues in antiretrovirals will render the tissues less susceptible to HIV acquisition. In clinical practice, this means that if you take the drugs every day, you have an excellent chance of preventing acquisition of HIV.
But there are other problems with inconsistent use of PrEP. One potential consequence of taking the pills intermittently is that drug resistance mutations can develop, which would undermine the effectiveness of the preventive strategy. This was only rarely seen in the PrEP trials, and we don't really know how that might affect acquisition risk or the risk of transmitting a drug-resistant strain in real-life settings.
We also don't know the consequences of taking these drugs as short-term postexposure prophylaxis or as immediate PrEP. That is, there are no studies that tell us whether it can reduce acquisition risk if you only take PrEP immediately after sex or just before sex.
Looking ahead, long-acting injectable antiretrovirals could make a difference in adherence for both treatment and prevention. There are trials underway in both HIV-positive and HIV-negative people, and this approach could reduce problems with adherence -- as long as patients go back to the clinic for their next injection. We've seen with contraception that injectable or implantable contraceptives are often more effective than oral contraceptives because they eliminate the need for daily adherence to the regimen.
Adherence, Adherence, Adherence
Medscape: How do we educate potential PrEP candidates about the importance of adherence?
Dr. Cohen: All we can do is educate individuals about what we've learned from the trials that were done. The PrEP trials demonstrated the biological plausibility that continually bathing the tissues in antiretrovirals will render the tissues less susceptible to HIV acquisition. In clinical practice, this means that if you take the drugs every day, you have an excellent chance of preventing acquisition of HIV.
But there are other problems with inconsistent use of PrEP. One potential consequence of taking the pills intermittently is that drug resistance mutations can develop, which would undermine the effectiveness of the preventive strategy. This was only rarely seen in the PrEP trials, and we don't really know how that might affect acquisition risk or the risk of transmitting a drug-resistant strain in real-life settings.
We also don't know the consequences of taking these drugs as short-term postexposure prophylaxis or as immediate PrEP. That is, there are no studies that tell us whether it can reduce acquisition risk if you only take PrEP immediately after sex or just before sex.
Looking ahead, long-acting injectable antiretrovirals could make a difference in adherence for both treatment and prevention. There are trials underway in both HIV-positive and HIV-negative people, and this approach could reduce problems with adherence -- as long as patients go back to the clinic for their next injection. We've seen with contraception that injectable or implantable contraceptives are often more effective than oral contraceptives because they eliminate the need for daily adherence to the regimen.
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